1. Field of the Invention
The present invention relates to a golf club, particularly to an improvement in the construction of a portion for connecting a golf club-head and golf club shaft.
2. Description of the Related Arts
Generally, a neck member of a golf club-head is provided with an elongated hole formed from the upper end toward a point midway in the neck member, and the lower end portion of a golf shaft is inserted into the elongated hole to connect the shaft with the neck member of the club-head. In such a case, a reinforcing core member is fitted into the lower end portion of the hollow shaft to improve the strength of the portion connecting the shaft and the neck member of the club-head.
In the conventional construction of such a connecting portion, since the hollow golf shaft is inserted into the elongated hole of the neck member, and the reinforcing core member is fitted into the lower end portion of the shaft, the strength of the neck member in which the shaft is inserted is very high. However, because of the presence of the elongated hole formed in the neck member, the sectional area of the neck member in which the shaft is inserted, and that of the neck member positioned beneath the lower end of the shaft, is radically changed, and thus stress is concentrated at the boundary surface defined by the base of the elongated hole, with the result that, upon impact with, for example, a golf ball, the neck member may fracture at that boundary surface.
Further, there is a recent trend for golf club-heads to be made of a light metal having a low specific weight, for example, aluminum, to increase the hitting surface area of the club-head. Such a club-head made of light metal has a low resistance to impact, compared with a club-head made of, for example, soft iron or stainless steel. Accordingly, the neck portion beneath the lower end of the golf shaft has a relatively low strength, with the result that this portion is easily fractured at the boundary surface thereof.